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Adaptations to Arid Habitats


What is an arid habitat? Arid habitats:  are extremely dry  receive little or no rainfall  usually have high temperatures  may suffer periodic droughts


Where are arid habitats found? Estimates suggest that arid and semi arid habitats account for more than one third of the earth’s land surface

Credit: U. S. Geological Survey


What are the challenges of living in an arid habitat? Lack of plants

Lack of water Challenges?

Lack of food

Temperature Movement Cold

Hot


What is adaptation? “the process whereby a species evolves characteristics that enable it to survive in a particular habitat”  Adaptations allow species to live successfully in their habitat  Species living in different habitats need different adaptations  Adaptations can be behavioural or physical


Barrow Island: Case Study - Approximately 70 km off the coast of Western Australia - Receives an average of 320 mm rainfall per year - Most of the island is covered by spinifex grassland - Nearly 2,600 different species have been recorded here


A flooded channel on the west coast of the island, a rare and important source of freshwater on Barrow


Mammals on Barrow Island Common wallaroo (Macropus robustus) Found across most of Australia, with one subspecies on Barrow Island Seeks shelter in caves and rocky outcrops Can go for a few months without drinking Licks saliva onto forearms to help it lose heat through evaporation Stops breeding during prolonged droughts, but breeds quickly in good conditions


Other mammal examples Wild Bactrian camel Many adaptations to conserve water, cope in intense heat and survive sandstorms!

Bat-eared fox Large ears to help dissipate heat


Fawn hopping mouse Can obtain water from seeds Produces concentrated urine + dry faeces Shelters in a burrow during day

Kangaroo rats ‘Nasal counterflow system’ reduces water lost through breathing


Amphibians on Barrow Island Main’s frog (Litoria maini) Only amphibian species found on Barrow Island Spends the dry season underground in a state of torpor Produces a membrane over the skin to prevent drying out Only emerges after rainfall Eggs laid in temporary pools, tadpoles develop quickly


Other amphibian examples Spotted marsh frog Shelters under logs and stones in the heat of the day

Water holding frog Can reabsorb water stored in its bladder or pockets under the skin

Green tree frog Takes refuge in any available water sources, including pipes, water tanks and toilet bowls!


Reptiles on Barrow Island Perentie (Varanus giganteus) General adaptations common to reptiles Shelters underground or in rock shelters; basks in sun in early morning and late afternoon On very hot days, may shelter in shade or climb termite mounds or shrubs to get off hot ground


Other reptile examples Thorny devil Tiny grooves over body direct moisture to the mouth Can change colour depending on temperature

Desert tortoise Dormant during hottest part of summer (aestivation) Lives in burrows


Eastern sandfish Streamlined body allows it to ‘swim’ through sand

Saudi fringe-fingered lizard Fringes of elongated scales on the toes help in moving across sand

Sidewinder ‘Sidewinding’ movement across loose sand


Plants on Barrow Island Spinifex grass (Triodia species) Extensive root system to collect water both from the surface and underground. Roots can be up to 3 metres long. Leaves have a waxy, impermeable surface (cuticle) to reduce water loss. Leaves curl inwards into long pointed tubes to slow the rate of transpiration.


Other plant examples

Lava cactus Stores water in thick stems, leaves reduced to spines to reduce transpiration

Grandidier’s baobab Stores water in trunk which can expand after rainfall

Bristlecone pine Parts of the living tissue die back during drought. Can still produce cones and seeds when conditions improve


Activity 1 You will be given a worksheet with a list of adaptations species use to survive in arid habitats. Your task is to decide whether each adaptation is a behavioural or a physical adaptation.


Activity 1 - Answers Adaptation

Behavioural?

Being nocturnal

Physical?

Impermeable skin

Producing concentrated urine

Aestivation

Panting

 

Ability to withstand high body temperatures Seeking shade

Ability to store water inside the body

Light colouration

Living in a burrow

Large surface area

Leaves reduced to spine

Breed only after rainfall Nasal counterflow

 


Summary • Arid habitats are dry areas with little rainfall and are usually hot, although they can be cold at night. • Arid habitats cover over a third of the Earth’s land surface. • Animals and plants have evolved a range of adaptations to help them survive in arid habitats. • These adaptations can be behavioural, such as sheltering in a burrow during the heat of the day, or physical, such as having a large surface area to lose heat more quickly.


Activity 2 The aim of this activity is to compare how effective different adaptations are at helping a species to conserve water. You will be given sponges soaked in water to represent your arid “animals�. You need to design an experiment to measure how much water your sponges lose under various conditions set up to represent different adaptations. You need to weigh the sponges before and after the experiment so that you can record how much weight (water) each has lost.


Adaptations to arid habitats classroom presentation